There are polymerizable compositions that include, for example, a polymerizable compound having an ethylenically unsaturated bond and a photopolymerization initiator. Since such polymerizable compositions cure when exposed to light, they are used for photocurable inks, photosensitive printing plates, color filters, photoresists and the like.
In recent years, combined with the demand in various applications for polymerizable compositions having sensitivity with respect to a short wavelength light of especially 365 nm, compounds that exhibit excellent sensitivity with respect to a light source of short wavelength, for example, a photopolymerization initiator, have been increasingly desired.
Use of oxime ester derivatives as a photopolymerization initiator in such polymerizable compositions has been proposed (see, for example, U.S. Pat. Nos. 4,255,513 and 4,590,145, Japanese Patent Application Laid-Open (JP-A) Nos. 2000-80068, 2001-233842, 2006-342166 and 2005-202252). However, since these known oxime ester compounds exhibit low absorbance with respect to light having a wavelength of 365 nm, there has been room to improve the exposure sensitivity with respect to light of this wavelength.
In view of the above, novel oxime ester derivatives, which exhibit increased absorbance with respect to short wavelength light of approximately 365 nm, improved sensitivity and favorable stability, have been proposed in recent years (see, for example, JP-A Nos. 2007-269779 and 2009-191061). However, these oxime ester derivatives still have a problem to be solved in terms of temporal stability, due to hydrolysis that occurs at an oxime ester site when these derivatives are used in a highly acidic or basic polymerizable composition.
There is also a strong demand for increasing the color density and reducing the thickness of color filters for image sensors for the purpose of enhancing the light-condensing capability of a solid-state image sensor such as a CCD image sensor or improving the image quality by enhancing the color-separation capability of the solid-state image sensor.
In order to increase the color density, a synergist that can interact with a pigment or a dispersant that can interact with the synergist is used together with the pigment. As an interactive group, an acid-base ionic interaction is generally widely used. When a large amount of acidic or basic substituents are present in the polymerizable composition in order to achieve a high color density, hydrolysis of the oxime ester derivative in the composition may occur and the temporal stability of the polymerizable composition may deteriorate.
Further, when a large amount of a colorant is added in order to achieve a high color density, sensitivity may not be sufficient to precisely reproduce the shape of fine pixel patterns having a size of 2.5 μm or less. As a result, there is a tendency for a lack of patterns to occur frequently in the entire region. In order to prevent the lack of patterns, the light exposure needs to be carried out with energy of a higher level. Therefore, the time for exposure may become longer and decrease in yield of products may be significant.
In consideration of the above, there is a need for polymerizable compositions used for forming a colored region of a color filter that exhibit high curing sensitivity, while containing a colorant and a dispersant at high concentrations, in order to attain an ability of forming a favorable pattern. There is also a need for polymerizable compositions that do not cause hydrolysis of an oxime ester derivative, while containing a dispersant having an acidic or basic substituent, in order to avoid decrease in sensitivity during storage over time.
A method is known in which occurrence of scumming due to residues or the like during a development process to form a color filter by adding an organic carboxylic anhydride having a molecular weight of 800 or less to a photopolymerizable composition for a color filter (see, for example, Japanese Patent No. 3,610,626). However, Japanese Patent No. 3,610,626 does not teach or suggest improving the temporal stability of a polymerizable composition. Therefore, improvement in temporal stability of a polymerizable composition including an oxime ester derivative as an initiator, the composition being capable of forming a highly precise image with high sensitivity, has been demanded.